1. Field of the Invention
The present invention relates to a disc player such as a CD player, a CD-ROM player or the like for vehicles, and particularly to a locking mechanism for selectively enabling a vibration-proof construction for resiliently supporting a drive unit on a chassis in a locked or unlocked state.
2. Description of the Prior Art
Generally, the CD player for vehicles has a vibration-proof construction for movably supporting a drive unit having a pickup, a turn-table or the like loaded thereon on the chassis through a resilient member, and is designed so that when operating in a reproduction state, the disc is not disturbed by external vibrations. In this case, when the drive unit is resiliently supported while carrying the disc, if the drive unit is moved by the external vibrations, the disc being carried may collide with the drive unit and be damaged. So, a locking mechanism has been employed in which when the disc is not mounted on the drive unit, the vibration-proof construction is placed in a locked state, and the drive unit is fixedly supported on the chassis (an example of which is disclosed in U.S. Pat. No. 4,628,498).
The locking mechanism for the disc player described in the aforementioned patent is provided with a rotatable roller bracket having a drive pin, a rotatable arm member having a cam surface, and a slide member capable of being moved forward and backward having an engaging groove; the roller bracket, the arm member and the slide member being mounted on the side plate of the chassis which resiliently supports a drive unit. A drive roller for carrying a disc is supported on the roller bracket, and the roller bracket rotates when the disc is carried onto the turn-table of the drive unit to move the drive roller away from the disc. The drive pin provided on the roller bracket is in contact with the cam surface of the arm member, and the arm member is rotated in association with the rotation of the roller bracket. The arm member is connected with the slide member through a protrusion and a slot, and when the arm member rotates, the protrusion of the arm member moves within the slot of the slide member whereby the slide member moves in a longitudinal direction. The engaging groove provided in the slide member is opposed to the protrusion provided on the drive unit, and when the slide member moves in a longitudinal direction, the engaging groove is engaged with or disengaged from the protrusion.
In the locking mechanism described above, when the disc is not mounted on the drive unit, the engaging groove of the slide member is engaged with the protrusion of the drive unit at the background position, and the drive unit assumes a locked state in which the former is fixedly supported on the chassis. When the disc is mounted in the locked state, the disc is carried onto the turn-table of the drive unit by the drive roller, but since at that time the drive unit is fixedly supported on the chassis, the disc is prevented from colliding with the drive unit. When the disc is carried onto the turn-table, the roller bracket rotates to move the drive roller away from the disc, and the drive pin moves along the cam surface of the arm member whereby to rotate the arm member, in association with which the slide member is moved from the backward position to the forward position. As a result, the engaging groove of the slide member is moved away from the protrusion of the drive unit to assume an unlocked state so that the drive unit is resiliently supported on the chassis along with the disc, thus preventing the reproduction state of the disc from being disturbed by external vibration.
The aforementioned conventional locking mechanism poses a problem that since the arm member and the slide member are mounted on the side plate of the chassis in an overlapping manner, when the rotational motion of the arm member is converted into the linear motion of the slide member, the arm member and the slide member rub against each other to impede smooth operation. So, it is contemplated that the arm member and the slide member are arranged within one and the same plane along the side plate of the chassis. However, since the cam surface formed on the arm member and the drive pin of the roller bracket should always be placed in contact with each other, it is difficult to miniaturize the arm member, and as a consequence, the entire disc player is prevented from being formed in a thinner configuration.
In accordance with the present invention, cam portions in which a drive pin of a roller bracket traces are put in an arm member and a slide member whereby when the drive unit is locked, the cam portions are brought into communication with each other, and when the drive unit is unlocked, the cam portions are separated from each other. With this construction, a part of the full length required for the cam portions is borne by the slide member, and therefore, miniaturization of the arm member itself and the rotational area thereof is possible so that the entire disc player can be formed in a thinner configuration; and further, when the drive unit is locked, the drive pin engages with the cam portion on the slide member side, thus enhancing the locking force.